A modified wetted-wall cyclone using different methods of water injection techniques upstream of the inlet was designed as an improvement to a wetted-wall cyclone developed by White, which uses liquid injection through a port on the wall of the cyclone inlet. The new cyclone has a high aerosol sampling flow rate (1250 L/min) and maintains constant cut-point with the modified White-type cyclone along with greater collection efficiency, lower time response, and reduced pressure drop. The final air-blast atomizer cyclone (AAC2.1a) design considered has an aerosol-tohydrosol collection efficiency cut-point of 1.3 mm with collection efficiencies at 1 and 2 mm of 39.9% and 86%, respectively. The efficiency reported for the modified White-type cyclone for particle sizes of 1 and 2 mm was 40.5% and 76.3%, respectively, under no water bypass conditions. The aerosol-to-aerosol transmission efficiency for the AAC2.1a configuration was found to be approximately 53.7% for 1 mm diameter particles as compared with 67.2% for the modified White-type cyclone. Dry and wet time response tests were performed in which the modified White-type cyclone had an initial response of 2.5 minutes for a wet start and 1 minute for a dry start for a condition where there was no liquid carryover through the cyclone outlet. The rise time for AAC2.1a cyclone under dry and wet start conditions was 0.5 minutes and 1.3 minutes, respectively. The decay response of the modified White-type cyclone was 1.1 minutes for a wet start and 1.2 minutes for a dry start. The corresponding numbers for AAC2.1a cyclone were 1.4 minutes for a dry start and 1 minute for a wet start condition. Off design tests were run at approximately ±10% air flow rates to see the effect on cyclone performance. It was seen that at a 10% higher flow rate (1350 L/min) the efficiency was 54.3%. At a 10% lower flow rate (1125 L/min) the efficiency was 33.7% as compared with an efficiency of 39.9% at 1250 L/min for 1.0 mm PSL particles. It was found that at a water input of 0.8 mL/min the efficiency reduced to 79.3% as compared to 86% at an input flow rate of 1.6 mL/min for 2 mm size PSL.

To ensure effective detection of bio-particles, it is crucial to understand the effects of collection method and archiving conditions on the survivability of bioaerosols, consequently, the survivability of the spore-forming Bacillus globigii (BG) and MG1655 Escherichia coli (E. coli), was determined after collection. The survivability was defined as the culturable fraction of the archived bacteria/culturable fraction of the as-collected bacteria. The bacteria were aerosolized for up to four days at room temperature (RT, 25 degrees C) and at 4 degrees C and collected in a 100 L/min wetted wall cyclone (WWC) and a 12.5 L/min SKC BioSampler. Aqueous solutions of 0.01% Tween-20 and 30% Ethylene Glycol (EG), with or without 0.5% ovalbumin (OA), were used as the collection fluids. Antifoam B (A-F), at a concentration of 0.2% (V:V) was added to the BG samples containing OA. In general, samples archived at 4 degrees C showed higher survivability than at RT. The survivability were more stable in EG than in Tween-20 especially for BG, very likely due to the surfactant effect of the Tween-20, which would remove the spore coat and initiate germination. In the WWC, adding OA significantly increased the survivability of BG in EG and in Tween-20, especially at RT. Similar effect of OA was found for E. coli samples stored in EG, suggesting that OA might be beneficial in maintaining the survivability. Adding A-F increased the survivability of BG in EG. In the SKC, neither the addition of OA nor A-F seems to have a beneficial effect on the survivability of the spores in EG samples. The best collection fluid for maintaining survivability in the WWC is EG+A-F for BG, and EG+OA for E. coli. However, in the SKC, EG is the best for BG collection and Tween-20 for E. coli. Viability transfer ratios, VTR, (cells surviving collection at time zero/viable cells aerosolized) were calculated for both devices. A performance ratio was calculated as the VTR of the WWC/VTR of the SKC. The geometric mean of the performance ratio is 1.51+/-0.83 for BG and 2.60+/-0.16 for E. coli, indicating that viability transfer ratio of the WWC is typically higher than that of the SKC.

In this study, a system for the collection of bioaerosols emitted from the mail sorting process was designed and characterized. Two different wetted-wall cyclones, the JBPDS cyclone and the glass cyclone sampler (GCS), were evaluated as system collection devices. These devices operate at 780 L/min and have a D50 of ~ 1 μm. A trimming impactor with a D50 of 10 μm was used upstream of the collection devices. Using two reference probes, the cyclone liquid outputs were compared with aerosol collected on filters and the output of an Aerosol-to-Hydrosol Transfer Stage (AHTS). The mass emission rate of the postal sorting machine was 3.15 mg/min and found not to vary significantly with flow rates above 700 L/min. On average, greater than 66% of the mass collected had a Da < 10 μm. Using a Coulter Counter, the volume median diameter (volume equivalent) for both device hydrosol outputs was 4.18 μm. For the effluent aerosol, the volume median diameter was 12.5 μm. For a bioaerosol release, this study found that greater than 65% (by volume) of the material released had a Da greater than 7.2 μm. Using filters, it was found that on average, 95% of the bioaerosol particles emitted had a Da less than 10 μm. According to the reference data, the expected number of bioaerosol particles in 1.5 times that collected by the GCS and 5.5 times that collected by the JBPDS cyclone for a one milligram release. The time constant for the system in response to a letter release was found to be 1.3 minutes for the GCS and 1.75 minutes for the JBPDS cyclone. A final note to this study states that the probe dimensions were incorrectly developed, therefore affecting the aspiration efficiency of the probes. In turn, this may have affected the outcome of some of the results. A plot is given at the end of the paper showing to what extent the results may have been affected. It is recommended that further experimental studies be performed to verify the results in this study.

This work includes wetted wall column experiments that measure the CO₂ equilibrium partial pressure and liquid film mass transfer coefficient (kg') in 7, 9, 11, and 13 m MEA and 2, 5, 8, and 12 m PZ solutions. A 7 m MEA/2 m PZ blend was also examined. Absorption and desorption experiments were performed at 40, 60, 80, and 100°C over a range of CO₂ loading. Diaphragm diffusion cell experiments were performed with CO₂ loaded MEA and PZ solutions to characterize diffusion behavior. All experimental results have been compared to available literature data and match well. MEA and PZ spreadsheet models were created to explain observed rate behavior using the wetted wall column rate data and available literature data. The resulting liquid film mass transfer coefficient expressions use termolecular (base catalysis) kinetics and activity-based rate expressions. The kg' expressions accurately represent rate behavior over the very wide range of experimental conditions. The models fully explain rate effects with changes in amine concentration, temperature, and CO₂ loading. These models allow for rate behavior to be predicted at any set of conditions as long as the parameters in the kg' expressions can be accurately estimated. An Aspen Plus® RateSep™ model for MEA was created to model CO₂ flux in the wetted wall column. The model accurately calculated CO₂ flux over the wide range of experimental conditions but included a systematic error with MEA concentration. The systematic error resulted from an inability to represent the activity coefficient of MEA properly. Due to this limitation, the RateSep™ model will be most accurate when finetuned to one specific amine concentration. This Aspen Plus® RateSep™ model allows for scale up to industrial conditions to examine absorber or stripper performance. / text

This work is a multi-scale effort to confront the rapidly evolving threat of biological weapons attacks through improved bioaerosol surveillance, detection, and response capabilities. The effects of bioaerosol release characteristics, transport in the atmospheric surface layer, and implications for bioaerosol sampler design and real-time detection were studied to develop risk assessment and modeling tools to enhance our ability to respond to biological weapons attacks. A simple convection-diffusion-sedimentation model was formulated and used to simulate atmospheric bioaerosol dispersion. Model predictions suggest particles smaller than 60 micrometers in aerodynamic diameter (AD) are likely to be transported several kilometers from the source. A five fold increase in effective mass collection rate, a significant bioaerosol detection advantage, is projected for samplers designed to collect particles larger than the traditional limit of 10 micrometers AD when such particles are present in the source distribution. A family of dynamically scaled wetted-wall bioaerosol sampling cyclones (WWC) was studied to provide bioaerosol sampling capability under various threat scenarios. The effects of sampling environment, i.e. air conditions, and air flow rate on liquid recovery rate and response time were systematically studied. The discovery of a critical liquid input rate parameter enabled the description of all data with self-similar relationships. Empirical correlations were then integrated into system control algorithms to maintain microfluidic liquid output rates ideally suited for advanced biological detection technologies. Autonomous ambient air sampling with an output rate of 25 microliters per minute was achieved with open-loop control. This liquid output rate corresponds to a concentration rate on the order of 2,000,000, a substantial increase with respect to other commercially available bioaerosol samplers. Modeling of the WWC was performed to investigate the underlying physics of liquid recovery. The set of conservative equations governing multiphase heat and mass transfer within the WWC were formulated and solved numerically. Approximate solutions were derived for the special cases of adiabatic and isothermal conditions. The heat and mass transfer models were then used to supplement empirical correlations. The resulting semi-empirical models offer enhanced control over liquid concentration factor and further enable the WWC to be deployed as an autonomous bioaerosol sampler. / text

Fossil fuel and advanced industrialization techniques contribute to global warming through emissions of greenhouse gases such as CO2. In order to mitigate climate change, there is a desperate need to reduce CO2 emissions from different sources. CO2 capture and sequestration (CCS) play an important role in these reductions. Naturally occurring enzymes, e.g., carbonic anhydrase (CA), can catalyze these reactions in living systems. Much effort has been focused on complexes of zinc with ligands such as teta, cyclen and tripodal ligands including BIMA and Trispyrazolylborates. These complexes have many interesting CO2 capture properties, but maintain toxic perchlorate ions. We desired to replace them with less hazardous counteranions like BF4- or PF6-. Our research focused mainly on the synthesis and characterization of Zn, Co and Cu cyclen and teta complexes that could mimic CA. We also examined some of these species for catalytic CO2 hydration behavior on wetted-wall column (WWC) at Center for Applied Energy Research (CAER). We successfully synthesized and characterized eight new complexes. These catalysts as CO2 capture systems are more stable have low molecular weights (compared to CA) and more cost effective than enzymes. In terms of catalytic activity significant results were obtained only for few of the catalysts